[e2e] Internet packet dynamics
touch at ISI.EDU
Tue Mar 30 09:54:40 PST 2004
Craig Partridge wrote:
> In message <Pine.GSO.4.58.0403161332180.17431 at stimpy.eecis.udel.edu>, "Armando
> L. Caro Jr." writes:
>>First, I don't see how it is possible to distinguish congestion induced
>>outages from non-congestion induced outages. Maybe it's possible in some
>>scenarios if the sender tracks delay variations similar to how FAST TCP
>>does, but this technique probably won't work with flash crowds.
> You can make a very good estimate using two pieces of information.
> First, a router knows what fraction of packets arrive trashed (e.g., CRC
Packets can get lost in the ether altogether (e.g., channel fade) or get
dropped at the NIC if the CRC fails (some NICs don't count failed CRCs;
the CRC is used to sync to the stream, so all background noise and
silence ends up equivalent to a failed CRC).
> Second, the router knows what fraction of packets it is dropping on the floor.
> So you can begin to infer the components of the loss rate.
> Craig Partridge
> Chief Scientist
> BBN Technologies
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